From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de, rostedt@goodmis.org,
linux-kernel@vger.kernel.org, kan.liang@linux.intel.com,
acme@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@redhat.com,
namhyung@kernel.org, ak@linux.intel.com, eranian@google.com,
brouer@redhat.com
Subject: Re: [PATCH 4/6] perf: Optimize get_recursion_context()
Date: Fri, 30 Oct 2020 18:11:38 +0100
Message-ID: <20201030181138.215b2b6a@carbon> (raw)
In-Reply-To: <20201030151955.187580298@infradead.org>
On Fri, 30 Oct 2020 16:13:49 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> "Look ma, no branches!"
>
> Cc: Jesper Dangaard Brouer <brouer@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
Cool trick! :-)
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
> kernel/events/internal.h | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> --- a/kernel/events/internal.h
> +++ b/kernel/events/internal.h
> @@ -205,16 +205,15 @@ DEFINE_OUTPUT_COPY(__output_copy_user, a
>
> static inline int get_recursion_context(int *recursion)
> {
> - int rctx;
> + unsigned int pc = preempt_count();
> + unsigned int rctx = 0;
>
> - if (unlikely(in_nmi()))
> - rctx = 3;
> - else if (in_irq())
> - rctx = 2;
> - else if (in_serving_softirq())
> - rctx = 1;
> - else
> - rctx = 0;
> + if (pc & (NMI_MASK))
> + rctx++;
> + if (pc & (NMI_MASK | HARDIRQ_MASK))
> + rctx++;
> + if (pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))
> + rctx++;
>
> if (recursion[rctx])
> return -1;
>
>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply index
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-30 15:13 [PATCH 0/6] perf: Reduce stack usage (and misc bits) Peter Zijlstra
2020-10-30 15:13 ` [PATCH 1/6] perf: Reduce stack usage of perf_output_begin() Peter Zijlstra
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 2/6] perf/x86: Reduce stack usage for x86_pmu::drain_pebs() Peter Zijlstra
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 3/6] perf: Fix get_recursion_context() Peter Zijlstra
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 4/6] perf: Optimize get_recursion_context() Peter Zijlstra
2020-10-30 17:11 ` Jesper Dangaard Brouer [this message]
2020-10-30 20:22 ` Steven Rostedt
2020-10-30 22:14 ` Thomas Gleixner
2020-10-30 23:31 ` Steven Rostedt
2020-10-31 11:23 ` Peter Zijlstra
2020-10-30 23:01 ` Peter Zijlstra
2020-10-31 12:11 ` David Laight
2020-10-31 13:18 ` David Laight
2020-11-09 12:12 ` Peter Zijlstra
2020-11-09 14:14 ` David Laight
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 5/6] perf/arch: Remove perf_sample_data::regs_user_copy Peter Zijlstra
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
2020-10-30 15:13 ` [PATCH 6/6] perf/x86: Make dummy_iregs static Peter Zijlstra
2020-11-10 12:45 ` [tip: perf/urgent] " tip-bot2 for Peter Zijlstra
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